A light emitting device is a semiconductor device that converts electrical energy into light such as infrared lays, visible rays, and ultraviolet rays using a characteristic of a compound semiconductor. A typical example of the light emitting device is a light emitting diode (LED). The LEDs are widely used for home appliances, a remote controller, an electronic display board, a display device, a variety of automation apparatuses, and the like and classified into an infrared emitting diode (WED) and a visible light emitting diode (VLED).
A blue LED is structure to include a sapphire substrate. An N-type GaN layer is formed on the sapphire substrate and an N-metal is formed on a portion of the N-type GaN layer. A portion except for the portion on which the N-metal is formed defines an active layer.
A P-type GaN layer is formed on the active layer and a P-metal is formed on the P-type GaN layer. The active layer is a light emitting layer that generates light by the combination of holes transmitted through the P-metal and electrons transmitted through the N-metal.
Meanwhile, a liquid crystal display (LCD), which is one of flat panel displays, is a device that varies optical anisotropy of the liquid crystal by applying electric field to the liquid crystal having both a liquidity property of liquid and an optical property of a crystal. The LCD has been widely used as it has a variety of advantages over a cathode ray tube (CRT) in power consumption, a thickness, a screen size, and a superfine display.
The LCD includes an LCD panel, a backlight, a printed circuit board (PCB), and a module holder. The LCD panel includes a lower substrate on which a transparent electrode pattern and pixel electrodes are connected to switching elements and an upper substrate on which common electrodes are formed. Liquid crystal is filled in a space defined between the upper and lower substrates. The backlight is a light source for emitting light to the LCD panel. An LED panel manufactured by an array of LED packages is generally used as the backlight.
The PCB includes a power supply/control module such as an integrated power module. The module holder includes a rectangular frame for fixing the above-described elements.
FIG. 1 is a side sectional view of a conventional LED panel 10.
Referring to FIG. 1, a PCB 15 on which light emitting devices 12 and conductive lines 14 are formed is attached on an inner lower portion of a rectangular frame 11. A molding layer 13 for dispersing the light of the light emission elements 12 is formed inside the frame 11. A diffusing plate 16 is attached on a top of the frame 11. At this point, a distance between the diffusing plate 16 and the light emitting devices 12 is greater than 5 mm to increase the luminescence.
In the above-described LED panel 10, the light that is diffuse-reflected toward the light emitting devices 12 can not be utilized. In addition, since the distance between the diffusing plate 16 and the light emitting devices 12 must be maintained above 5 mm, it is difficult to reduce the weight and thickness of the LED panel 10.
In addition, when intensity of the current applied to the light emitting devices 12 increases to generate high output light, the heat dissipation performance in the package is not good to generate heat in the package. When the internal heat is not effectively dissipated, the resistance increases to deteriorate the light efficiency.
Particularly, the conventional LED panel 10 is designed such that the light emitting devices 12 that emit light in a specific direction (e.g., in an upward direction) are independently arranged without the light interference between them, it is difficult to display white light that can be realized by mixing red (R), green (G) and blue (B) colors.